Asian Gypsy Moth
Lymantria dispar asiatica
Adult female. Photo: John H. Ghent, USDA Forest Service, Bugwood.org
Adult male on tree trunk. Photo: John H. Ghent, USDA Forest Service, Bugwood.org
Egg masses on bark. Photo: John H. Ghent, USDA Forest Service, Bugwood.org
Gypsy moth caterpillar with distinctive rows of red and blue dots. Photo: John H. Ghent, USDA Forest Service, Bugwood.org
The Asian gypsy moth is an exotic insect pest native to Far East countries such as Russia, China, and Japan. Adult moths frequently lay their egg masses on cargo ships and shipping containers, and these hardy egg clusters often survive to hatch at ports of call around the world, including the United States. The first such known introduction was in 1991, where egg masses on a Soviet ship docked in Vancouver were found to be hatching. Due to fear that the larvae could have blown onshore, efforts to detect and identify any Asian gypsy moth introductions in the Northwest were made. During the summer and fall of that year, Asian gypsy moth was found in Vancouver BC, Portland OR, and Tacoma WA, and these local populations were eradicated quickly. Since 1991, there have been 20 introductions of Asian gypsy moth in the U.S., all of which were eradicated successfully.
Unlike the European gypsy moth, which is closely related but has a more restricted host range, Asian gypsy moth females are active fliers, capable of flying up to twenty miles. Therefore, the Asian gypsy moth could quickly spread throughout the United States.
The only way to tell Asian gypsy moth apart from European gypsy moth is with DNA tests.
Asian gypsy moth eggs are found in large masses attached to solid outdoor objects such as trees, stones, lawn furniture, and logs. They are covered with buff or yellowish fuzz and average about 1½ inches long and ¾ inch wide, though they can be as small as a dime.
Caterpillars emerge in the spring and feed until June or July when they enter the pupal stage. Adult moths emerge 10 to 14 days later. Male gypsy moths have grayish-brown wings with a wingspan of about 1½ inches. Adult females are white and much larger, with wingspans of approximately 3½ inches.
In high enough densities, Asian gypsy moths can completely defoliate host trees causing severe physiological stress and can result in the death of the tree if defoliation occurs several years in a row or in conjunction with other natural stresses such as drought. Large numbers of caterpillars, and their resulting droppings and silk strands can also be a nuisance in residential areas. Asian gypsy moth caterpillars have voracious appetites; feeding on over 500 tree and shrub species. An introduction could lead to significant plant losses in forests, orchards, and landscapes.